From what I’ve seen, this has to be one of the most, if not the most detailed post on this issue. Since I’m having the same issue, I’m going to try to follow @squad8’s path, with @Quench’s directions and explanations, and get it resolved (preferably before that part in the post where I would need to get my hands on an oscilloscope).

Switch 17 is on. TP1 is the ground and is 0. TP2 is 4.7. TP3 is -12.6.

So this checks out so far right?

I have the jumper wire.

2 for 2 right?

Okay this just got real difficult real quick. Not sure how to test the MPU J4 for this signal changing state.

Okay now I’m 2 for 4, as I’m not sure how to go about getting eprom’s burned, as I don’t have the computer set up and/or devices to do it myself. Is anyone selling them already programmed?

No speech in test mode or in game. When pin is booted up it will sometimes mumble a couple syllables. Also when it is on and I remove and replug the J3, it will also make a blurting sound.

I found some on amazon. What about this one: Elenco Electronics Lp-560 Logic Probe Electronics Testing Tool

Perfect. If it comes with a tutorial, I'm getting it. Thanks.

Is there a way to check this jumper wire to verify that it is operational. I am assuming using the DMM on ohms to do a continuity check from one end of the wire to the other. If I see “resistance” in the form of Ohms does that tell me that the wire is installed properly? Thanks

Here is the back of the SBU and the VSU

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Not sure if I am testing it right b/c I put the DMM on ohms (levels between 200 and 200k). I put one end on J3-5 and the other on the top of C14. The DMM is automatically at 1 with no contact. When contact is made, it reads at some number e.g. 12 on level 20k, and then goes down to 0 and stays there.

Here are close ups:

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I got the logic probe, and started probing around the IC’s with the pin in attract mode, and just noted the signal, I.e. high, low, or pulse. With this information alone, would I be able to determine anything useful? One thing that I noted, for example, is that of all the pins on the IC’s only one results in a “sound” when contact is made with the logic probe (which is like a hum/buzz of sorts). Does that mean anything useful? Thanks

And it was right there, right under my nose, all along. Went to probe this pin, but noticed that it wasn’t there? Went to my notes from these threads, and I had a note that MPUJ4-11 should go to VSU J3-5. But, on my pin it looks like VSU J3-5 is going to MPU J4-9. I moved the wire from J4-9 to J4-11, and “one, two, three” etc. !!!

So i am posting the before and after photos. It reminds me of a concept I like very much: Sometimes a small change can make a big difference.”

Thank you to everyone for all your input.

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And so the back glass finally goes back on.

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I wanted to go into the schematic to confirm the MPU J4-11 pin function, but am seeing “NU”. Is that a mistake in the schematic?

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